Hitherto, magnesium compounds such as magnesium chloride and magnesium alkoxides have been widely used as a support material without being milled in the field of catalysts for olefin polymerization, specifically the monopolymerization or copolymerization of olefins such as ethylene and propylene. This may improve the catalyst activity and the morphology of polyolefin powder.
For example, for improving an olefin polymer in the morphology including a particle size, form, etc., JP-A-S63-280707 discloses a method in which a magnesium compound is supported on an inorganic oxide such as silica, or JP-A-S58-000811 discloses a method in which a magnesium compound is once dissolved in a solvent such as an alcohol and then precipitate again, which precipitate is used.
However, these methods include very complicated steps, since they require the procedures of supporting, dissolving and precipitating a magnesium compound. Further, these methods have a defect that the catalyst is poor in stability of performance since the catalytic activity is high only at an early stage of the polymerization.
JP-A-H4-130107 discloses to use as a support of catalysts a magnesium compound obtained by reacting metallic magnesium, an alcohol and a certain amount of halogen. However, the sphericity or particle size distribution of support and polymer powder obtained may not be satisfactory dependently on the particulate properties of metallic magnesium or conditions under which a magnesium compound is produced.
In view of the foregoing the invention has been made and an object thereof is to provide a magnesium compound, a solid catalyst component for olefin polymerization, a catalyst for olefin polymerization and a method for producing a polyolefin, which can give a polyolefin with a narrow particle size distribution and/or a nearly spherical form without reducing stereoregularity and catalyst properties such as polymerization activity.
The inventors made efforts to find that the above subject can be solved by producing a solid catalyst component for olefin polymerization by reacting a magnesium compound and a titanium compound, the magnesium compound being obtained from metallic magnesium with a specified sphericity or particle size distribution index, or merallic magnesium with an oxidized coating film having a specified thickness; or obtained by reacting metallic magnesium with a specified average particle size, a specified amount of an alcohol and a halogen and/or a halogen-containing compound under specified stirring conditions. The invention has been completed by the finding.